Aircraft instrument



Sept. 6, 1949. H. B. MARIS AIRCRAFT INSTRUMENT Filed July 24, 1945 3 Sheets-Sheet l 5O 4O 30 ZOIO O vii INVENTOR Harr- B- Map-Ls BY ATTORNEY Sept. 6, 1949. H. B. MARIS 2,480,867

AIRQRAFT INSTRUMENT Filed July 24, 1943 3 Sheets-Sheet 3 INVENTOR Harry E. Maris ATTORNEY fiatented gept. 6, 1949 AIRCRAFT INSTRUMENT Harry B. Maris, Riverdale, Md., assignor to the United States of America. as represented by the Secretary of the Navy Application July 24, 1943, Serial No. 495,994

12 Claims.

(Granted under the act of March 3, 1883, asamended April 30, 1928; 370 O. G. 757) The invention relates to improvements in aircraft instruments and more particularly to vertical indicators and sighting devices for use in conjunction with aerial photography and the dropping of bombs from aircraft.

An important object of the invention is to provide an aircraft bank indicator of economical design and construction.

Another important object of the invention is the provision of an instrument which will indicate angles of bank up to 90 with increasing accuracy as the angle of bank increases, when the aircraft is flying in curved balanced flight.

A further object resides in the provision of mechanism for supporting an aerial camera with its axis vertical during curved balanced flight of an airplane.

Yet another object is to provide means for supporting a bomb sight in a stabilized position relative to the ground during curved balanced flight of an airplane.

A still further object is the provision of a bomb sight with means compensating for various flight conditions, such as ground speed, altitude and wind velocity.

Other objects and advantages of the invention will become apparent during the course of the following detailed description, taken in connection with the accompanying drawings, forming a part of this specification, and in which drawings,

Figure 1 is a View partlylin side elevation and partly in central vertical longitudinal section of an instrument embodying the principles of the present invention,

Figure 2 is a View in front elevation of the instrument with portions thereof broken away,

Figure 3 is a View similar to Figure 2 but illustrating the relationship of parts when the airplane is in curved balanced flight,

Figure 4 is a diagram of the forces acting on the instrument to dispose its parts as shown in Figure 3, g i I Figure 5 is a horizontal sectional view of a sighting device embodying the principles of the invention, the view being taken substantially on' the line 55 of Figure 6., V V

Figures 6, 7 and 8 are vertical transverse sec-. tional views taken substantially on their respective lines in Figure 5,

Figures 9 and 10 are plan views of differently delineated screens for use with the sighting device shown in Figures 5-8.

In the drawings, whichshow alternate forms of the invention, and wherein similar reference 2 1 characters denote corresponding parts throughout the several views, the letter A generally designates the improved bank indicator and B, the sighting device.

Referring more particularly to Figures 1-3 of the drawings, the bank indicator A includes a bracket Hl'carrying spaced parallel arms H, E2 and It. The bracket I0 is secured to a portion l4of an aircraft so as to extend in the direction of the vertical axis of the aircraft and with the arms ll, l2 and I3 extending in the direction ofthe longitudinal axis of the aircraft. Formed in the arms l2, l3-are axially aligning openings l5, l6 slidably receiving a normally vertical rod ll resiliently connected at its upper end to the arm I l,as by an expansion coil spring l8 having an unextended length l. Fixed to the lower end of the rod ll is a weight l9 extending the'spring l8 a distance d due to gravity when the rod I1 is in its normally vertical position.

- Carried by the arm I2 is a normally horizontal frame 20 defining an opening 2| in which a camera 22 is mounted for swinging movement transversely of the airplane, as by axially aligning pivots 23, 24. The axis of the pivots 23, 24 extends in the direction of the longitudinal axis of the airplane and is normal to the longitudinal axis of the rod ll. Formed in an exterior 'wall vertical.

of the camera 22 is a rectilinear slot 25 tangent to an are r whosecenter lies on the axis of the pivots 23, 24 and whose radius equals the distance d of extension of the spring [3.

Perpendicularly fixed to the rod I1 is a pin 26 normally intersecting the are r and slidably fitted in the rectilinear slot 25. The camera 22 may be suitably balanced for swinging movement about the pivots 23, 24, as by a Weight 27. If desired a scale 28 may be provided for indicating in degrees the angular relation of the rod I? to the camera 22.

Assuming the aircraft to be flying level and on a straight course, the instrument A will occupy the position shown in Figures 1 and 2, wherein gravity and the spring l8 exert equal but opposite forces on the rod H, and the pin 26 floats halfway between the ends of the slot 25 so as tomaintaln the axis of the camera 22 During a turn requiring banking of the airplane at an angle 0 to maintain balanced flight, the bracket in participates in the banking movement so that the longitudinal axis of reciprocation of the rod IT is rotated. The camera 22 of course tends to remain with its optical axis vertical due to inertia. Referring more particularly to the diagram shown in Figure 4, the force of gravity 9 on the rod and weight acts downwardly along the vertical axis MM and the centrifugal force generated by the curved balanced flight acts laterally or normal to the axis i'M- M, The resultant force f facts in the direction of theaxis N-N defined by the angle 0. Since the resultant force f is greater than the force of gravity y, the spring i8 is extended beyond the distance d and -the pin =25 moves along the slot 25 away from the axis of the pivots 23, 24, by an amount just sufio'ient to maintain the position of the camera22 in space. Thus, the angle between the rod l7 and the camera 22 as indicated on the scale -2-firis' the angle of bank of the aircraft while in curved balanced flight.

Referring now to Figures 15-1 0 of the drawings, the sighting device B illustratedthereinis so constructed as to operate in accordance with the principles of operation of the bank indicator A. In addition the sighting device B includes means compensating for various conditions encountered during horizontal aircraft bombing operations, such as aircraft speed, elevation and wind velocity. Mounted for swinging movement about an axis transversely of the aircraft, as by pivots 29, 30 secured to portions 3| of the-aircraftand provided with anti-friction bearings 32, 33, is an outer gimbal frame 84. Mounted for swinging movement about an axis longitudinally of the aircraft, as by pivots 35, 35 rotatabl-y carried by the outer gimbal frame 34, is an inner gimbal frame 31. Thisframe 37 is to be maintained parallel to the ground, when the aircraft is in curved balanced flight, by means hereinafter described, responsive to the force of gravity and to centrifugal force.

Suspended beneath the outer :gimbal frame 34 as by cables 38-41, one at each corner, is a rectangular weight 42, guided for sliding movement toward and away from the outer gimbal frame 34, as by rods 43 fixed to the outer gimbal frame 34 and extending through openings in the corners of the rectangular weight 42. The cables 38, 39 are attached to one side of the weight 42 and are secured to spools -44, 45 fastened on a -shaft 46 rotatably supported by the outer gimbal frame 34. The cables 40, 41 are attached to the opposite side of the weight 42, pass over pulleys -41, 48,-on the outer gimbal frame 34, and are secured to the spools 44, 45. Secured to one'end of the shaft 46 is the inner end of a spiral spring 49 having its outer end attached to a cylindrical case 54 releasably fixed against rotation relative to the outer frame 34, as by a dog -5l.

Extending downwardly from opposite sides of the inner gimbal frame (3-1, as shown more particularly in Figures 6 and 8,are depending aprons 52, 53 each provided along its lower marginal edge portion with a rectilinear outwardly facing groove 54. Rigidly secured to opposite sides of the weight 42 at the mid-points thereof are pins 55 extending into and slidable along the grooves 54.

Mounted for rotation about the transverse axis of the airplane, as by pivots 56,, 51 :carried by cross-bars 58, 59 forming part of the inner gimbal frame 31 is an annular frame 54 releasably securable in any one of a plurality of angularly adjusted positions with respect to the innergimbal frame 31, as by a sector 6| fixed forswinging movement with the annular frame 50.. Extending through an arcuate slot 62 in the sector is asset screw 63 fastened to the cross-bar 59 as by nut 64. Supported in the annular frame 60 is a ro- .4 tary member 65 provided with a worm wheel 66 meshing with a worm 61 fastened on the shaft (58 of a variable speed reversible motor 69.

Mounted for movement radially of the rotary member 65 along a suitable slot 10 therein, is a carriage Til provided on opposite sides with racks 12, T6, meshing with pinions l4, l5 "pivoted on the rotary member 65. Also meshing with the pinions 14, 15 are racks 16, T! reciprocably mounted in the rotary member 65 and carrying weights 18, as shown more particularly in Figure 8, for balancing the rotary member 55 in any radially adjusted position-ofthe carriage l i. Fixed in a perpendicular opening 19 extending through the carriage, "as by screw threaded engagement therewith is a tubular lens holder as carrying a plate 8"! covering the slot 19 so as to prevent the entrance -of light into the camera when the lens holding carriage ii is in any position of adjustment relative to the slot Ill. Secured to the annular frame 5.5 is an inverted frusto-conical tube 82 supporting a ground glass viewing screen 83 in elevated parallel relation to the frame 50. Fastened to the carriage ii is a light 84 focused on a point centrally of the screen 83 when the carriage H is centered in the rotary member 55, as shown in Figure 6.

The strength of the spring 49 and the size of the rectangular weight 4.2 are so chosen that the gravity pull on the weight 42 will unwind the cables Sit-4| from the shaft 45 .a distance equal to the distance between the axes of the pivots 35, 36 and the pins '55. Exact adjustment of the length of the cables 38-4! is made in order to dispose the weight 42 at a level just sufficient to freely support the pins 55 in the slots 54. This adjustment may be made by rotating the spring case 59 and clamping the case in adjusted position by means of the dog 5i. Thus the conditions specified for g in the bank indicator A shown in Figures 1-4 are similarly met in the sighting de vice B; movement of the pins '55 along the-grooves 54 will measure 0 as in Figure 4; and the length of the cables "38-4l unwound from the shaft 45 during operation of the device will measure I. Whenever the plane is in balanced flight so that the direction of is parallel to the vertical axis of the plane, the distance the pins 55 have moved along the grooves 54 will be a measure of the centrifugal force and the inner gimbal frame '31 will be maintained horizontal; The pivots 29, 3'0 permit swinging movement of the outer gimbal frame 34 about an axis transversely of the airplane so that the frame 34 may remain horizontal during steady forward flight although the longitudinal trim of the aircraft may vary due to changes in the amount or location of the cargo or passenger load carried by the aircraft.

The ground glass viewing screen 83., as shown in Figure 9, is provided with a plurality of circles 85-95 and arcs iii-34 of varying radii each tangent to a longitudinal diametrical line at its center 96, the centers of the circles and arcs lying on a transverse diametrical line '9! passing passing directly over the object on the ground. The circle described by the image will be tangent to the longitudinal line 95 and its center will lie on the transverse line 91. In bombing operations, this would be a target circle with zero lead, and all such circles would be tangent to the longitudinal line 95 with their centers lying along the transverse line 91.

In the utilization of the device B as a bomb sight, the annular frame 60 is fixed at an angle relative to the inner gimbal frame 3! corresponding to the dropping or range angle determined by the aircraft speed and elevation at which the bombing operations are to be performed. The device may be used at various speeds and altitudes by providing a set of screens delineated. for the various dropping or range angles. vInFigure is shown a viewing screen 83a designed for a predetermined dropping or range angle. This screen is provided with a transverse line 98 in parallel relation to adiametrical transverseline 99, the distance therebetween depending on the dropping or range angle. A circle I09 and 'arcs IDI-l 12 are drawn from centers lyingon the transverse line 98 so as to intersect at the center H3 and at a point H4 on the longitudinal diametrical line H5. If no windcorrection is required, bombing target images will appear at the center H3 of "the screen 83a when the lens carriage H is centered relative to the rotary member 65. By piloting the plane in curved balanced flight so that the image of any ground target describes on the screen 83a a circle passing through the center H3, the airplane may be brought into bombing position relative to the ground target. The circle described by the target image on the screen 8311 will not be tangent to but will intersect the longitudinal line H5 at the point H3. The centers of all target; circles will lie on the line 98 parallel to the transverse diametrical line 99 but displaced from it by a distance fixed by the lead angle.

The wind correction vector which determines the radial distance that the lens holding carriage H should be displaced from the center of the rotary member '65 to compensate for the wind velocity, may be computed from the wind velocity and aircraft elevation. The arrangement of the pinions I4, is such that, as the carriage H is shifted for wind correction purposes, the weights 18 are oppositely moved so that the device will remain in balance. In this connection, it will be noted that the motor 69 is located opposite the spring case 50, relative to the center of the device, and the masses of these members are so selected that they compensate one another in order to provide substantially perfect balance. If necessary, a weight H6 may be fastened to; the inner gimbal frame member 59 in order to, completely balance the gimbal frame 31 and parts carried thereby. Since the light 84 is focused on the center H3 of .the screen 83a when the lens is centered relative to the rotary member '65, displacement of the light image fromthe center will indicate the magnitude and directionof the wind correction.

An airplane in uniform circular flight with reference to the air will follow a prolate cycloidal path with reference to the ground providing its air speed is greater than the wind velocity. The minor radius of the cycloid will be proportional to the wind velocity and the major radius will be proportional to the plane speed through the air. If the airplane follows a circular path with reference to the ground, these conditions will be approximately reversed with reference to the air path. The wind correction serves two purposes, first to displace all images on the screen 83a to compensate for the wind correction whereby any image at the point I 13 on the screen will indicate a-target in bombing position and second, to guide the aviator in selecting a' cycloidal path of flight relative to the ground, while flying along a circular path relative to the air which will bring him into bombing-position forany chosen target. If the wind direction at the instant of release of a bomb were known in advance, the proper wind corrected cycloid could be delineated on the screen to assist in training the pilot in approaching a target while turning in a Wind.

After the carriage H has been shifted to compensate for the magnitude of the wind correction vector, the aviator introduces the wind direction into the sighting device B by operating the motor 69 so as to orient the rotary member 65 whereby the direction of the light spot relative to the center of the screen 83a corresponds with the wind direction. The speed of the motor 69 is regulated and set so that the rate of turn of the rotary member 65 carrying the lens holder is the same as that of the airplane but in the opposite direction. Thus the position of the light relative to the center of the screen constantly indicates the magnitude and direction of the wind correction vector during circular balanced flight of the aircraft relative to the air, and also indicates the phase of the cycloida1 path along which any chosen image is traveling onthe screen.

Although screens having cloids delineated thereon flight conditions would be of use in training pilots, their employment in actual bombing operations would be extremely limited, if not impractical. However, the pilot, after utilizing such screens for training purposes and after becoming sufliciently familiar with the relationship between the circular image paths delineated on the screen 83a as designed for still air and the cycloidal paths followed by the images during circular flight in a wind, will, from the position of the wind correction vector on the screen 83a, be able to visualize, against the back ground of circles and arcs on the screen, the cycloidal path along which the image should move in order to reach bombing position.

Various changes may be made in the forms of the invention herein shown and described without departingfromthe spirit of the invention or the scope of the following claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

In an instrument for indicating the vertical during balanced turning flight of an airplane, a bar provided at one end portion with a weight, means for guiding the bar for longitudinal movement in the direction of the normally vertical axis of the airplane, a member provided with a guideway, means for pivotally securing said member in neutral, balanced equilibrium for swinging movement about an axis extending longitudinally of the airplane and with a point along said guideway tangent to an arc whose center lies on said longitudinal axis, said guideway normally extending horizontally and at right, angles to said longitudinally extending wind corrected cyfor predetermined axis, an element carried by said bar and'slidably associated with said guide-way, and resilient means normally supporting the bar against longitudinal movement with said element aligning with said tangent point and withsaid resilient means normally strained by said bar and weight a distance substantially equal to the'distance between said longitudinal axis and said tangent point.

2. In an instrument for indicating the vertical during balanced turning iiight of an airplanaa bar provided at its lower end portion with; a weight, means for guiding the bar for longitudinal movement inthe direction of the normally vertical axis of the airplane, a member provided with a guideway, means for pivotallysecuring said me bar in neutraL balanced equilibrium for swinging movement about an axis extending longitudinally of the airplanewand with a point along said guideway tangent toan arc whose center lies on said longitudinal axis, a pin fixed on said bar and s idable along said guideway, said 'guideway normally extending horizontally and at right angles to said longitudinally extending axis, and a spring connected to the bar'anri nnrmahy sup orting the bar against longituclmal movement with said pin aligning with said tangent point and with said spring normally strained by said bar and weight a distance substantially equal to the distance between said longitudinal axis and said tangent point.

3,. In an instrument for indicating the vertical during balanced turning flight of an airplane, a bar provided at its lower end portion with a weight, means for guiding the bar for longitudinal movement in the direction of the normally vertical axis of the airplane, a member provided with a giudeway, means for pivotally securing said member inneutral, balanced equilibrium for swinging movement about an axis extending longitudinally of the airplane and with a point along said guideway tangent to an arc whose center lies on said longitudinal axis, said guideway normally extending horizontally and at right angles to said longitudinally extending axis, a pin fixed on said bar and slidable along said guidcway, and an expansion coil spring con nected to the bar at its upper end portion and normally supporting the bar against longitudinal movement with said pin aligning with said tangent point and with said spring normally strained by said bar and weight a distance substantially equal to'the distancebetween said longitudinal and said tangent point.

4. In an airplane instrument of the character described, an-element having a rectilinear guideway, means pivoting said element in neutral, balanced equilibrium about an axis extending longitudinally of the-airplanewitha point along said guideway tangent to an arc :whose center lies on said longitudinal axis, said guideway normally extending horizontally and at right angles to said longitudinally extending axis, a weight, means guidin the weight for movement ver ticaily of the airplane, means transmitting movement of the weight to said element including a pin slidable in said guideway, and a spring nor-, mally supporting said weight with said pin aligning with said point of tangency and with said spring normally strained by said weight an amount equal to the distance between said tangent point and said longitudinal axis.

5. In a device of the character described, an outer gimbal frame, means pivotally supporting the outer gimbal frame for swinging movement about an axis aex'tendingtransverselyof an airplane, a weightmeans normal to the outer-gimbal frame foriguiding the weight toward and away from-said frame, an imier'gimbalframe, means pivotaliy supporting the inner gimbal frame in neutral,- balaneed-equilibrium for swinging movewent about an axis normal to the pivotal axis of said outer gimbal frame, said inner gimbal frame provided a guidewayhaving a point tangent to an arc whose center lies on the pivotal axis oisaid inner frame, said guideway normally extending: horizontally and parallel to said transversely extending axis, a pin movable with said weight and slidable along said guideway, me'silicnt means carried by the outer gimbai frame' for normally supporting the weight against movement relative to the outer gimbalframe with said piu aligning withsaid tangent point and with said resilient imeaus normally strained by said'weight: a distance substantially equal to the distance betweensaid' longitudinal axis and said tangentpoint.

a In a ide'vice of the character described, an outer gimbal framezmeans adapted to be carried by an airpianefor pivotally'supporting the outer gimbalirame for swinging movement about an axis 'inr-thenormally horizontal plane of the airplane and transversely thereof, a weight, means normal to the outer gimbal frame for guiding the weight toward and away from said frame, an'inner gimbal frame;means pivotally supporting the inner gimbal frame in neutral, balanced equilibrium for swinging movement aboutam axis normal to the pivotal axis of saidouter gimbal frame, said inner gimbal frame provided witha guideway 'having a point tangent-to an arc whose center-lies on the pivotal axis of said inner" gimbal frame, said guideway normally 'extending horizon'tallyand parallel to said transversely extending axis-an element movable'with said weight and slidable along said guideway, resilient means carried by the outer gimbal frame for normally "supportingthe weight against movement relative to the outer gimbal frame with said element aligning with said tangent point and with said resilient means normally strained by said weight a' distancesubstantially equal to the distance between said longitudinal axis'autl said tangent point,

"7. In a sight adapted to be maintainedina'level position in an airplane, a supporting frame, a support, means 'carrieclbythe iram'efor pivotally securing the'support to the frame for angular swinging movement about an axis transversely of-th'e direction of travel of the airplane, means releasably-fixing the support relative to the frame in any one of a plurality of angularly adjusted positions, rotary means carried. by said support for "rotation about an axis normal tosaid transverse axis, and a sight member supported bysaid rotary means for movement transversely of I said rotary'mea'ns.

8. Ida sight adaptedto be maintained in a level position in anairplane, a supporting frame, a support, means carried by the frame for pivotally securing the support to the frame for angular swinging movement about an axis transversely'of'the direction of=travel or the airplane, means releasably fixing the support in any one of a plurality oi'angularly adjusted positions relativefto' the frameyrotary means carried by said support :ior rotation about an axis normal to said transverse axis, a sight member, means supporting the sight member 'for movement 75 transversely of said-rotary means into-any one of a plurality of positions of adjustment, and means for automatically balancing the rotary member with said sight member in any one of said positions.

9. In a sight adapted to be maintained in a level position in an airplane, a supporting frame, a support, means carried by the frame for pivotally securing the support relative to the frame for swinging movement about an axis extending transversely of the direction of travel of the airplane, means for fixing the support relative to the frame in any one of a plurality of angularly adjusted positions about said transverse axis, a carriage, means securing the carriage to said support for rotation about an axis normal to said transverse axis, a lens holder, means mounting the lens holder in said carriage for lateral movement transversely of said carriage, a screen provided with circular delineations defining arcuate segmental areas constituting image paths of ground objects during curved balanced flight of the airplane, said paths terminating at one end in a point centrally of the screen, and means securing the screen to said support and so positioned above the lens holder as to display images of ground objects in said arcuate segmental areas.

10. In a sight adapted to be maintained in a level position in an airplane, a supporting frame, a support, means carried by the frame for pivotally securing the support relative to the frame for swinging movement about an axis transversely of the direction of travel of the airplane, means fOI fixing the support relative to the frame in any one of a plurality of angularly adjusted positions about said transverse axis, a carriage, means securing the carriage to said support for rotation about an axis normal to said transverse axis, a lens holder, means mounting the lens holder in said carriage for lateral movement transversely of said carriage, a screen provided with circular delineations defining arcuate segmental areas constituting image paths of ground objects during curved balanced flight of the airplane, said paths terminating at one end in a point centrally of the screen, means securing the screen to said support and so positioned above the lens holder as to display images of ground objects in said arcuate segmental areas, and means for indicating the relative position of said screen with respect to said lens holder.

11. In a device of the character described ineluding a lens holder adapted to be maintained with its axis vertical in an airplane during curved balanced flight thereof, a viewing screen provided with circular delineations defining arcuate segmental areas constituting image paths of ground objects during curved balanced flight of the airplane, said paths terminating at their ends in a point centrally of the screen, and means so positioning the screen above the lens holder as to display images of ground objects in said arcuate segmental areas.

12. Apparatus for detecting change in the attitude of a body relative to the earths radius, comprising means mounted to swing detectably about a normally horizontal axis relative to the body, and means for maintaining said firstmentioned means in a predetermined position relative to the earths radius, including reciprocable pendulous means having a weight W, means carried by the first-mentioned means for defining a rectilinear path of reciprocation of said pendulous means lying at distance L below and perpendicular to said axis, said pendulous means including spring supporting means therefor having a rate substantially equal to W/L and adapted to exert force transversely of said pathdefining means and upon said first-mentioned means when said first-mentioned means departs from said predetermined position, said pathdefining means and said pendulous means cooperating to eifect restoration of said first-mentioned means by exertion of said force on the latter, to said predetermined position in response to departure of the first-mentioned means therefrom.

HARRY B. IVIARISL REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,152,946 Hasburg Sept. 7, 1915 1,296,640 Estoppey Mar. 11, 1919 1,446,280 Titterington Feb. 20, 1923 1,837,609 Carter Dec. 22, 1931 FOREIGN PATENTS Number Country Date 316,167 Germany Jan. 28, 1920 

